Signal assembler comprising a delay line and shift register loop



1965 J. H. HELFRICH 3,166,734

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CLEAR Jan. 19, 1965 .1. H. HELFRICH 3,166,734

SIGNAL ASSEMBLER COMPRISING A DELAY LINE AND SHIFT REGISTER LOOP Filed Dec. 6, 1962 9 Sheets-Sheet 5 I F/G. 48

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J. H. HELFRICH SIGNAL ASSEMBLER COMPRISING A DELAY LINE Jan. 19, 1965 AND SHIFT REGISTER LOOP 9 Sheets-Sheet 7 Filed Dec. 6, 1962 o mm m QOWWMUOQO ERR-Wu Gk 1965 J. H. HELFRICH 3,166,734

SIGNAL ASSEMBLER COMPRISING A DELAY LINE AND SHIFT REGISTER LOOP Filed Dec. 6, 1962 9 Sheets-Sheet 8 F 5 8/7 uvsmr ADV.

J. H. HELFRICH SIGNAL ASSEMBLER COMPRISING A DELAY LINE Jan. 19, 1965 AND SHIFT REGISTER LOOP 9 Sheets-Sheet 9 Filed D66. 6, 1962 end in a loop configuration. V lected to achieveprecession in the loop, For example, if

- 3,166,734 SIGNAL ASSEMBLER COMPRKSENG A DELAY LINE AND SHIFT REGZSTER LOOP John H. Helfrich, Middletown, N.J., assignor to llell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York Filed Dec. 6,1962, Ser. No. 243,213 12 Claims. (Ci. 346-147) ing information such as On-hook, Off-hook, Call-waiting, Busy, Cancel and the like.

At the interface between a central switching ofiice and the transmission facility associated with'each incoming line or trunk, there must be interposed equipment which 3,166,734 i' atented Jan. 19, 1965 Precession again takes place as the S and S bits circulate around the delay loop so that the S bit reappears at the input one delay loop bit position before the introduction of the next S-bit (S When the 8;, hit is introduced into the delay loop it therefore appears immediately ad- 7 the input of the register in the manner described, anda can provide necessary compatibility. Thus, for example,

from incoming message streams to'a centralswitching oflice, this equipment must separate S-bits-from message and framingbi'ts, assemble the S-bits into S-cliaracters and" finally provide for the transfer of these assembled charactersto the central processor of the switching office. Conversely, for outgoing message streams from a central switching ofiice, the equipment must provide for the ac-. .ceptance'o'f S-characters from the central processor, the

distribution of the S-chara'cte'rs as S -bits to the terminating line equip outgoing message bit streams.

parallel read out from the same is carried outshortly after the last S-bit of each S-character has been read in, The assembled S-characters are then transferred in parallel form'to the central'processor. 1 V

It is a significantfeature of the invention that the same delayloop can be used for the assembly of -S-characters from a plurality of incoming subscriber lines, and/or trunks. By selecting the proper bit spacing in the delay line loop, a loop capacity can he arrived at for accomodating any given number of incoming lines. All line terminals are scanned for S-bits on a sequential and cyclic basis and these 'arestored in and read out of the delay loop as heretofore described. Thus, the assemblyof a plurality of unique ,S-characters is carried out more or less simultaneously. i

' In a further embodiment of the invention, the capacity of the delayloop is increased to accommodate two successive S-characters of each incoming multiplexed mes sage stream. This permits the temporary store of an ment, and finally-insertion of the S-bits into the Various methods and meanshave been devised heretofore to implement the'S-bit' assembly and distribution functions. The known schemes, however, all involve the use of extensive and complex storage equipment.

-S-characterwhilethe next successive oneof the same ine's'sage stream is assembled. As each new S characteris assembled, it is compared with the previous one, and if difi ?erent,"it'iis readout to. the central processor. successive S-c'haracters of a given, multiplexed message stream are the same, however, no such read out occurs.- Thus the signaling information is efiectively screened and the central processor is advised only of changes inthe If the same.

- Because of high costs usually entailedin the use of large I:

capacity stores, considerable'efforthas-been devoted to minimization of the store requirements 'Unfortunately, store requirements have not-been appreciably reduced of substantially inwithout encountering the penalty creased decision logic. I

It is accordingly an object of this invention to circumvent the above dilemma by resorting to dynamic storage techniques for the interchange ofsuper'v-isory information between a central switching'oflice and subscriber lines, or trunks. 7 A further object of the pres'ent'invention is to provide A supervisory signal-distributor constructed in accordance with the present invention likewise comprises a precessional delay loop-that includes a delay line and a shift register connected end to end in a closed loop configura tion. lThedistri-butor utiliies the same structure as" the assembler he'reto-foredescribed, but the readin and read out operations are reversed. That is, the S-char'acters highly flexible yet relatively simple and inexpensive proc- 1 essing circuits for supervisory information interchange;

A supervisory signal assembler-constructed in accordance with the principles of the present invention comprises a delay line and a shift registerconnected end to The total loop delay is sethe S-bits in the incoming message bit stream are located at a preassigned position in alternate sub-frames, a total loop delay equal to the duration of two sub-frames less one delay loop .bitspacing will provide the desired, precession. Accordingly, if the first S-bit (S of an S-cha r subsequent bit position immediately adjacent tot-he S bit.

designated" for respective outgoing message bit streams, aresuccessiv'ely read intothe shift register ofthe delay loop in parallelform,-;while the read out therefrom is a series or sequential one. The read out mayadvantageously take place at the input to the delay line. i

I The various features and objects of the-invention may be better understood by a consideration of the following detailed description when read in-connection withthe drawings in which:

FIG. -1 which is comprised of parts 1A and-1B placed as shown in EC, is a block diagram representation of a typical time division switchingsystem comprising the time division switching matrix, the line and/or trunkitermination circuits, and the supervisory signal assemblers and distributors; t

FIG. 2 illustrates a typicalmessage bit stream that is visory' signal assembler constructed in accordance with the present invention; j FIG; 4, which is comprised of parts 4A and 4B placed planation of the invention;

as shown in QC, illustrates waveforms useful in the exscriber line or'trunk.

", central'tirning'unit-(notshown); I 1 he TDS supervisory signal assembler;'receives superillustrate the manner of operation of the delay loop shown in FIG. 3;

FIG. 6 isa modification of the assembler of 3 wherein successive S-cha'ra'cters of each message bit stream are compared and readout of the same occurs only in response to a change in S-character coding;

FIG. 7 shows a series of symbolic diagrams that illustrate the manner of operation of the delay loop of HG. 6;

FIG. 8 shows a schematic block diagram of a supervisory signal distributor in accordance with the principles of Lnepresc'ntinvention; and

FIG. 9Iis a table useful in the explanation of the distributor of H6. 8.

Referring nowmore specifically to the drawings, there is shown inFlQ'la block diagram schematic of an illustrativejtime division switching system comprising a time division switchingfmatrix 8, line or trunk termination circuits 9 and assembler-distributor subsystems Zltl. As is known to those in the art, atime division switch (TDS) provides a facility that can multiplex digital messages under'the direction of a common control or central processor (not shown). Such systems have the capability of associating any pair of subscribers or trunks andmultiband trunk.

' I In response' to instructions received from the central processor, the switching matrix establishes the necessary connections {or transferring the message bits of an incoming subscriber line 1 or trunk to a given outgoing sub- The time division switch terminal 'circuits'j 'perforin 7 three basic functions. They (1') separate'the supervisory bits, from the'rness'age' bits in the incoming bit stream,

(2 buffer bothlthe message bits preparatory to theirbeing switched through the TDS matrix-and the'supervlsory I bits preparatory totheir entryjintothe TBS supervisory signal assembler, a'n" l[(3.) insert into the outgoing stream message bitsreceived through the TDS matrix and super visory bits received from the 'TDS supervisory signaldistributor." I

The digital messages from both Ways; thatis, toand j from subscriber lines, or trunks. Data 'arrives fr orn: a subscriber in a digital stream containing'rnessage and supervision, and each bit is stored,v egg, in a capacitor, in

the stripper portion of the TDS terminal circuit for apertio'riof bit'period. It is then transferred to a separation circuitxwhere, if it is a supervisorybit, it can be stored in one capacitor if amessage bit, stored in another,

. agaih for a'fraction ofa bit'period. The message bit is then transferred, by resonant transfer for example, to'

a capacitor in the digital hybrid where it awaits itsassigned. time slot tor transfer. through the mat X lLD the hybrid 'ofthe receiving' subscriber line or trunk.

sage bit stream, The control of thestripper' and inse'rter iisoryl bits horn allthestrippcrs andafter assembly of the i same into respective S-ch'aracte'rs it transfersthese ing the'signal assembler and distributor circuits of the present invention and for showing the interrelationship of the-"latter with the other units of a time division switch. The signal assembler and distributor circuits of theinvenj ti'on are of general utility and are inne Way limited to .any specific switching matrix 'or terminal circuitry, nu-

yFrorn' there it can; again 'beltransierred by resonanttransfer to theinserter; where it is' inserted into the outgoing Inesmerous arrangements and various modifications of the latter units being well known to those in. the art.

FIG. 2 shows the format of a typical digital message stream that is received over a transmission line in a cyclic pattern. in the illustrated case, a cycle of 136 bits, or a frame, contains 128 message bits; 4 supervisory bits 8;, S S and S which form a unique S-character; and 4 control bits, F F P and P The eight supervisory and control bits are called subfran're bits and, for ease and simplicity in processing, these are normally distributed evenly throughout the bit stream, any two adjacent subfrarne bits being separated by sixteen message bits. The F and F bits are framing bits, and the P and P bits may be used for parity check purposes. The message bits can constitute multiplexed message bits from a plurality of subscribers or, alternatively, the message bits of a single subscriber. In either event, the signal assembly and distributionfunctions are the same.

For illustrative purposes, four incoming and iour outgoing subscriber lines will be assumed, over each of which there can appear a digital message bit stream such as shown in FlG. 2. Typically, the digital data of the respective lines will be synchronized with each other under the control of a master synchronizing circuit (not shown) located eithe the central olfice or remotely. For simplicity in presentation such synchronization will be assumed herein. However, as will be clear hereinafter, subscriber line synchronization is not required by the assembler and distributor circuits of the present invention; all that is necessary is that the bit rate and bits per frame be the same for all lines.

Turning now to the supervisory signal assembler o -FlG. 3 and .the explanatory Waveforms of FIG. 4, the

S-bits that appear in each of the incoming synchronous message bit streams, designated S S S and S in FIG. 4, are. stripped therefrom and delivered to input terminals ll, 2t, 31 and (ll, respectively. Thus, the S-bits of bit stream S will be delivered to terminal ill, the S-bits of bit stream 5 to terminal 21, and so'on. 4 i

The S-bits appearing at the input terminals 21, 21, 3 and .1 are fed to the flip-flops 12;, 22, 32 and 42, respectively, via double rail gate logic circuits. The operation of these logic circuits is such that an input binary one sets the associated flip-flop toits l state, and a binary Zero sets the flip-flop to its 0 state. For example, a

' binary one S-hit at terminal ll will be applied to the input circuits is'acoomplihed by. driving the ,transferswitches' pulses ioflthe proper frequency and; phase from a r. i I

clock pulse generator (not shown). A typical generator for producing periodic clock pulses that are synchronous with the S-bits in the incoming bit streams is disclosed in the copending application of D. M. Cculter, Serial No. 208,647, filed July 9, 1962. Thus, with the two inputs of AND gate 13 momentarily energized, an enabling signal will be delivered to the- ;set terminal of flip-flop I22 to set the same to its 1 state If flip-flop 12. was already in the 1 state, it just remains there. Since the input cl-bit is inverted in inverter i l, the AND gate 15 remains deenergized at this time.

A binary zero S-bit at terminal ll fails, of course, to energizeAND gate but because of the voltage inversion provided by inverter 514, this binary zero causes an energizing signal to be delivered from AND gate 15 to the reset terminal of flip-nop 3 .2 to set the same to its 0 state.

in the described manner, the flip-flop i2 is continuously set and reset in accordance with the coding of the S-bits in the bit stream designated S And in similar fashion the flip-flops 22, 32., and 42 are set and reset in accordance with the 5-bit coding of bit streams S 5 and 5, respectively.

In response to the applieclS-bits, the flip-flops 12, 2.2, 32. and 32 assume the successive states illustrated by the FIG. 4 Waveforms designated'FF-ll, P5 22, FF-32 and El -42. Since each of the S-bits or the bit stream 5 is a binary one, the flip-flop 12 will be set to, and remain in,

its 1 state (see waveform FF-l2). A change in the S -character coding will, of course, alter this flip-flop output. The S and S bits of message bit stream S are assumed to be a binary one, while the S and 5., bits are both assumed to be a binary zero, the latter bits thus being illustrated in dotted form. Accordingly, the flip-flop 22 will beset to its 1 state and then to its 0 state on alternate half frames, as illustrated by the waveform FF- 22. The derivation of the waveforms FF-SZ and FF-42, which are indicative of the successive states of flip-flops 32 and 42, is believed self-evident from the foregoing explanation.

The successive states of each flip-flop therefore correspond to the sequence of S-bits in the message bit stream associated therewith. The assembly of S-bits is thus effectively carried out by sampling the flip-flop outputs, sequentially and cyclically, and delivering the samples to the delay loop for temporary storage. 1

The sampling of the flip-flop outputs, the read into storage of the same, the parallel read out from storage and various other operations are carried out under the control of the timing signal generator 30. The generator 3t? comprises a conventional binary counter 36 and associated logic circuitry. The counter itself consists of seven stages,

. each of which is designated with a designation in parenthesis indicating the decimal equivalent of the binary stage. Clock pulses from a local clock (not shown) advance the count in counter 36 in a typical step-like manner. The counter thereby normally counts and resets cyclically and in synchronisrn with the incoming frames. i

The input clock pulses to the counter and the output of various counter stages are shown in FIG. 4 of-the drawings. The clock pulses are illustrated by the waveform designatedADV. CLOCK. Every stage of the counter has a (1) and (0) output terminal, which are alternately energized. That is, when "the (1) output terminal of a stage is energized the-(O) terminal is deenergized and vice versa. I When the first clock pulse is applied to stage (1) of the i binary counter 36, thisstage will be setto its 1 state andwill provide an energizing signal-at its (1) output terminal. When the second clockpulse is applied. to binary 6 gized once every other subframe (i.e., once in each of the periods separating successive S-bits). Thus, if the flip-flop 12 is in its 1stage during a scan (i.e., when the (0) output terminals of. stages (8) and (16) are energized) a corresponding signal .will be read out to the. common bus 50. v

However, if the flip-flop 12 should happen to be in its 0 state, no AND gate output occurs and this, of course, is indicative of the 0 state of the flip-flop. i

The AND gate 27 is connected at its input toflip-flop 22, to the (1) output terminal of counter stage (8), and to the (0) output terminal of counter stage (16); .Thus, read out of the flip-flop 22 occurs once every other subframe during the period thatthe (1) output terminal of stage (8) and the (0) output terminal of stage (16) are energized. It will be seen from the waveforms of FIG. 4 that this read out follows the read out of flipflopllZ. In similar fashion, the read out. of flip-flop32 occurs during the period that the (0) output terminal of stage (8) and the (1) output terminal of stage (16) are energizedyand, the read out of flip-flop 42occurs during the period that the (1) output terminals'of counter stages (8) and (16) are energized. The flip-fiopsare thus scanned sequentially and cyclically to thereby provide a multiplexed signal on bus 50 such as that shown by the waveform of FIG. 4 designated SCAN-OUT. Since the output of the flip-flops is representative of the 8-bit coding of the respective message bit streams, the multiplexed pulse signals of the latterwaveform are given their appropriate S-bit designation. Thus, the first multiplexed pulse signal on bus- 50 corresponds to the coding of the 8 bit of bit stream S thenext succeeding multiplexed pulse on bus. 5tlris indicative ofthe coding of the S bitof bit stream S the next pulse is representative of the S bitof bitstream S and the next Q scanning recycles and signals indicative of the S bits counter 36, stage (1) will be set to its 0 state and stage In FIG. 4 the waveform designated (1)-1 represents the i signal that appears at the (1) output terminal of stage (1) in response to successive input clock pulses. The waveform (1)-0 represents the signal at the (6) output terminal of stage (1), and it is, of course, the inverse of the above.

-Waveform (2)-1 is the signal that appears at the (1) output terminal of stage (2); waveform (4)1 is the signal at the (1) output terminal of stage (4); and so on.

The subframe clock pulse generator, noted above, delivers a reset pulse to the counter 36 to initiate a,- cycle of counter operation.- This reset pulse is synchronous with the S bits of the message bit streams, and the same may be derived, for example, in the manner disclosed in'the abovecited. Coulter application. The reset pulses are shown inserted in the ADV. CLQCK waveform of FIG. 4; they are labeled Re.

The flip-flops are scanned sequentially and cyclically using'the output of stages (8) and (16) of counter 36 and the AND gates 17, 27, 37, and 47.1; For example, the (1) output lead" of counter 12 isi-connected to the input of of each bit stream are multiplexed onto bus 50; and so on. 1

The; (1) output of counter stage (1) is differentiated and the negative-going spikes are removed in ,the ditferentiator-clipper 48. Thus, a short duration positivegoing pulse signal is I provided at the output of the diifercntiator-clipper 43 each time the counter stage (1) is set to its 1 state. This short duration pulse signal is, therefore, generated'for every other input ADV. CLOCK pulse, as indicated bythe FIG.'4 waveform designated DIFFVOUT. v

The AND gate 49 is connected at its inputto the duferentiator-clipper 48, the 1) output terminal of counter stage (2), and the (0) output terminal of stage '(4) Thus,-the AND gate 49 passes the aforementioned positive-going pulse signals during those periods that the (1) output terminal of stage (2) and the (0)v.output,

terminal of stage are energized. I The output of AND gate 49 is illustrated by the FIG. 4 waveform designated ,-fSAMPLE. As thenarne' implies, the' short duration output pulses from :AND gate 49 sample the multiplexed'pulse signals appearing .oncommon bus 50 (compare waveforms SCANPOUT and SAMPLE). To

this end, the output pulses of gate 49- are fed to the input of AND gate 51 along with said multiplexed pulse AND gate 17. The input of this AND. gate is also connectedto the (0) output terminals of the stages (8),. and

(16) of the counter. Accordingly, thestate o f the flip-flop .12 will be read out tothe common bus Stleach time the (0) output terminals of stages (8) and (16) are energized. Turning new to FIG. 4 and particularly to the waveforms designated (8)-() and (16)-0, it will be seen that the (0) outputterminals of the stages (,8) and (16) are both enersignals. The sampled signal bits are then deliveredto the input of the dynamic storage meansfor temporary storage therein. L

Thedynamic storage unit comprises a four stage shiftregister 52 and a delay line Sis connected end-to end in a loop configuration, i.e., the output of the shiftregister is connected to the input of the delay line andthe output or shift the information stored therein. 'ister is advanced at arate four times the rate of read in of the sampled bits (compare the pulses of the Waveform the delay line, simultaneously (see'diagram f). I 1

7 The short duration pulse signals from the dilferentialclipper 48 are applied to the shift register 52 to advance The shift reg- DIFF. OUT with the pulses of the Waveform SAMPLE). Accordingly, a bit will be read out of the register, into with the insertion of a new bit intothe register. V w

Taking into account the shift rate and the delay'line length, the total delay in the delay loop should be such as to provide precession in the loop. For example, for the assumed'rnessage bit'stream format, a total loop delay "equal to the duration of two sub-frames less one bit spacing in the loop will provide the desired precession. Accordingly, if the first S-bit of an S-character (e.g., S 'is sampled and introduced into the delay loop, it will circulate around the loop and will reappear at the input one delay loop bit position before the introduction of. the next S-bit of the same'S-character (S Thus, when the, S bit is introduced into the delay loop it occupies a bit position immediately adjacent the S bit. Preces- 'sio'n'again takes place as the S and S bits circulate around the delay loop so that the- S bit reappears at the input onedelay-loopbit position before the introduction of the next S-bit-of the'S-character (S When the S bit is introducedinto the delay loop it therefore appears immediately adjacent the S bit which is in turn adjacent the S bit. This process continues until all the S-bits of the S-character are assembled in proximate bit positions inthe delay loopr the S-character is then read out-in parallel form. As will be clear from FIG. 5, the described assembly operation'is carried out simultaneously for each of the incoming message bit streams using the same delay loop. The delay loop and the manner ofoperation of the same are symbolically illustrated in FIG. 5.

The first four bit positions 54 represent the four stages of the shift registerSZ, while the remaining eleven positions 55 represe1it the. storage capacity ofthe delay line in terms of bit positions. 'Thus, the delay line isof a length such as't'oa-providea total delayequal to-eleven shift-pulse periods; The output of thedel'ay line is fed back to the input of the shiftregister via feedback pathSd.

In diagram a, thefirst S-bit (S of the bit stream S has: been inserted into the input stage of the shift register. Ass-described heretofore, the' shift register is shifted at a rate four times the rate of read in of the sampled bits and 'thus the S bit will be read out of the register, into the delay line, simultaneously with the insertion of'the next bit (S on bus 559 into the register (see diagram b).

This newbit, of course, represents the first S-bit of the 'bit stream S In the diagrams cand d the stored bits are advanced four bit positions'fo'r each new S-bit insertion (i .e., S 3 and's Considering now the diagram e of "FIGJSQthe 5 bit circulates around the delay loop and reappears at theinput'to the shift register one bit positioribeforethri introduction of the next sampled bit,

which isthe second S-bit (S of bit stream-S Stated somewhat differently, :if'the stored bits are advanced four bit positions for each neW' 'S-bit. insertion, the 81 bit will be shifted to the second stage of the shift register simultan-ously with the "insertion of 1116 5 bit.

I All of the stored bits are once again advanced four bit positions as the next sampled S-bi-t (S is introduced into the register Withthe' insertion of the S bit into the register the g 7 a The next bitftobe inserted into the delay loop isthe S bit of bitstream'S Which'completes the asscmbly of theS character of bit stream S ,(see diagram n).' In 75 similar fashion the S-characters of bit streams S and S are assembled, and the process thereafter repeats and assembly of the next succeeding S-character of each message bit stream begins.

As indicated in diagram 0 of FIG. 5, with the insertion of the S bit into the delay loop the latter is filled to capacity. From this point on each new bit to be inserted must displace or supplant a previously stored bit. For example, in diagram p the S bit is inserted into the delay loop in the position previously occupied by the 5 bit. However, in each instance, the displacement of an 8-bit is preceded by the read out of the same as part of an S- character. Accordingly, no usable information is destroyed in this displacement.

The inhibit gate $7 of FIG. 3 accomplishes the aforementioned bit displacement. The output of the delay line 53 is normally delivered to the input of the shift register 52 via the gate 57, except when a sampled S-bit is to be inserted into the register. To this end, the sampling pulses that are delivered to the AND 53 are also fed to the inhibit input of gate 5?. Thus, gate 57 is inhibited each time that gate 53 is energized and any S-bit previously circulating at this time is prevented from recirculating by the action of this inhibit gate.

If the delay line is subiect to minor variations in delay it may be best to inhibit the gate 5? over a short period of time which straddles the sampling pulse from gate 4%. Tothis end, the inhibit signal to gate 57 could instead be derived from an AND gate (not shown) whose input is connected to the (1) output terminal of stage (2) and the (0) output terminal of stage (4) of counter 36.

The readout signals are derived from AND gate 58, Whose input is connec ed to the (1) output terminals of stages (4), (32) and (64) of counter 36. The output of this gate is differentiated and clipped, as heretofore described, and the derived positive-going pulses are applied to the AND gates 59. The read out pulses comprise the EEG. 4 waveform designated READ OUT. Comparing this waveform and the Waveforms designated (4)4, (32)l and (64)l, it will be seen that a read out pulse is produced for each positive-going transient of waveform (4)1 that occurs during the period that the (1) output terminals of stages (32) and (64) are energized. As indicated by the Waveforms SAMPLE and READ GUT, the read out operation occurs shortly after the sampling and insertion of each S bit into the delay loop.

it Will be recalled that assembly of each unique S-char- Referring to FIGS. 3 and 5 of the drawings, it should be clear that the shift register 52 may comprise more than four stages. This, of course, would result in a corresponding reduction in the bit position storage capacity of the delay line. In fact, for the assumed numer of incoming bit streams it would undoubtedly be less expensive to provide a recirculating shift register of fifteen bit positions (i.e., fifteen stages) rather than the combined register delay line combination shown. However, for a large number of incoming bit streams 136 at a 4 3.8 lib. rate) economy calls for the use of a delay line and shift register combination such as that disclosed.

The length of the delay line will depend upon a number of factors such as the number of incoming subscriber 'ines and the bit rate of the same, the number of shift register sla es, the racticable bit 5 acin in the line. and

e P V the like. The only rigid requirement in thi regard is that the total loop delay be such as to assure precession in the loop.

The desired precession WHSilChlEVfid in the described case by providing a total loop delay equal to the duration of two sub-frames less one bit spacing. it will be clear,

times the rate of read in of the sampled bits; a

The delay loop and the manner of operation of the however, to those in the art that precession can also be achieved with a total loop delay equal to the duration of two sub-frames plus one bit spacing. The assembly operation is exactly the same as heretofore described, the only difference being in the order of the S-bits assembled in the register. This order is the reverse of that shown in diagrams in through p of FIG. 5. That is, the bits of each assembled S-character will be arranged in the register in an ascending order such as S S S S Furthermore, as indicated above, the message bit streams need not be frame or even sub-frame synchronized with each other for operation of the assembler of the present invention. All that is necessary in this regard is that the message streams be bit synchronous with each other and the frame rate and bits per frame be the same for all lines. Minor modification of the flip-flop read in circuitry would be necessitated, but the flip-flop sampling, the read into the register, and the advance and precession of the bits in the delay loop can be carried out the same as heretofore described. The readout operation similarly occurs shortly after each 8.; bit insertion into the loop, but since the latter may occur in some staggered fashion, the read out pulses wouldmost likely not be derived from a single counter unit as described. Individual line framers such as disclosed in the aforementioned Coulter application may, for example, be used to provide the necessary read out pulses. The use of such additional equipment on. a per line basis can be justified by the fact that line frame synchronization and the equip-' ment required to establish and maintain thesame may be eliminated. 1' '1, I Referring now to FIG..6 of the drawings, there is shown a modification of the FIG. 3 assembler, wherein successive S-characters of each message bit stream are compared and read out of the same occurs only in response to' a change ins-character coding. "The read in to. theflipflops 12, 22, 32 and 42, the scanning ofthe same, the bit sampling and insertion of'the samples into the delay loop, jet cetera, all take place as 'her'etofore'described. Accordingly, onlythe points of departure ofthe FIG. 6 circuit will be covered. V l

In. the circuitiof FlG. 6, the capacity of the delay loop is increased to accommodate two fsuccessiveS-characters of each incoming multiplexed message bit stream. This increased capacity is achieved herein byincreasingthe shift rate of register 52,.which effectively reducesfthe time slot or hit spacing the storedbitswithin theloop.

FIG. 7. Here again, the first four bit positions 54 repre-- sent the four stages of the shift register, while the remaining positions 55 represent the storage capacity of the delay line in terms of bit positions. The bit spacing in this delay loop is half that of the FIG. 3 arrangement as a result of the increase in shift rate, thus effectively doubling the delay loop bit capacity. The total delay offered by the loop is here again, equal to a double subfrarne interval :tlbit spacing.

'7 In diagram s of FIG. 7, the first S-bit (S of the bit stream S has been inserted into the input stage ofthe shift register. The shift register is shifted at a rate eight times the rate of read in of the sample bits and thus the S bit will appear at the position shown in diagram if when the next sampled bit (S is inserted into the register. In diagrams u and v, the stored bits are advanced eight bit positions for each new S-bit (i.e., S 3 and S insertion. In diagram w the stored bits are again shifted eight delay loop bit positions and hence the S bit will be shifted into the second stage of the shift register simultaneously with the insertion of the next sampled bit (S The S bit is thereby placed immediately adjacent the 8, bit and the assembly operation thus begins.

, The insertion of the 3, bit" into the register completes the'assembly of an S-character of message bit stream S However, because of the increased capacity in this p'recessional delay loop, assembly of the next succeeding S-cha'racter of the same message bit stream takes place immediately adjacent the preceding character, as-

illustrated in diagram z. For example, the inserted S bit will circulate around the delay loop and be shifted into the second-stage of the shift register simultaneously with the insertion into the first stage" of the sampled bit (8 of bit stream S As indicated in the S waveform of FIG. 4, the 8 bit .representsthe S' bit-or" the next su c-- ceedingS-character of bit stream S Thereafter, the as:

5 sembly of this next succeeding S-character is carried out in the manner explained above. Thus, each S -character is assembled as, described, and each assembled S-character If the bit spacing of the. stored bitsis reduced by half, 7

for example, then twice 'as many bits can be storedfin a given delay loop. However, as with the previously de-' scribed precessional assembler, theldelay loop must be one time slot or bitposition short of; (or longer than) a double subframeinterval sothat S-bits are advanced (or i.e., the S-bitsprecess as previously described. a The sampling of the 8-bit takes place'f'at the same retarded) one bit position during each loop circulation,

'rate and in the same manner as in.-the FIG. 3 circuit, but

the shift rate of register S2 is doubled." To this end, clock pulses at a rate twice the FIG. 3 clock pulse rateare applied to the input'of the divider stage 61. This stage may comprise a typical binary counter stage and hence an out put pulse signal willbe derived therefrom and delivered to the counter 36 for every other input clock pulse (i.e.,

stage 61 divides by two). The 1) output of stage M is differentiated and clipped, in the manner described heretofore, arid the derived short duration positive-going pulse signals are fed to the shift register 52 to advance or shift the data bits stored therein. From the foregoingit should; be clear that'the counter Edcounts and recycles at the'same'r'ateas in'FIG. 3, but theishift rate of the register 52 has now been doubled. The shift register is, therefore, advanced in'thisjernbodiment at a rate sight 'same aresyrnb-olically il lustra te d the diagrams of b s eam.

occupies a positionimmcdiately behind the preceding S -characterof the same'bitstream, as shown in diagram The s-charactersare eventually displaced by means of inhibit gate 57; however, ineach instance, the displacement of an S-character is preceded by a logical comparison'lbetwee'n it and the succeeding S character of the same Th lo' 'cal comparison of successive S-characters is carried out .byfthe read out inhibit circuit62. This read out inhibit serves to compare -,eacl 1 newly assembled S-character with the previously assembled character of V the same bit stream and if they are different, the new g, character is read-out to the central processor. If the} successive Scharacters of a given message bit stream are the same, however, no such read outoccurs. The signaling information is thus screened'and the central processor 'is only advised offchanges' in the same.

i The read out pulses that are derived from the Al lD gate53, in' the manner described*hereinbefore,"are deliv-,

eredto the read out AND gates 59 via the AND gate 63.

The other input toAND gate 63 isl'derived fromthe (1) output tern1'inal offiip-flop 64 Accordingly, with the iiip-flo'pfid set to its 1 state, the gate 63 wi11 be ener- 1 g'ized'to pass the read out pulses; whereas" withthe flipiioplsetlin its ()state, noread out pulses are passed by gate'63J A clear or reset signal is delivered to theilip-flop it will berecalled, completes the assembly of an S-character. Further, the insertion into the. register 52 0f each 9S bit ,will-be precededby -the reintroduction" into the f register of the circulating S S and S bits of the same S-characterL i j The clear signal is delivered 'to' the flip-flop 'd' jlist prior to the reintroduction into the shift register of the 64- will remain in its state.

f stantially the "sameas'in the assembler ;of FlG. 3.

I ,cordingly, onlythepoints of departure of FIG. Swill be eneeyrsa it it circulating S bit of the new S-character. This clear signal is derived from AND gate 65 which is coupled at its input to the counter 36 in the manner shown in FIG. 6. Now as the S bit is reinserted into the four stage register 52, the S bit of the preceding S-character of the same bit stream is shifted out. The exclusive-0r circuit 63 is connected at its input to the input and output terminals of the shift registerSZ. Exclusive-0r circuits are well known in the art and they serve essentially as matching cincuit 66 will deliver an energizing signal. to the flip-flop 64 to set the same to its 1 state.

i In a similar fashion the circulating S and S bits which are reintroduced into the register and the 8,, bit which is inserted into the register for'the first time are successively compared with the S S and 3,, bits, respectively, of the preceding S-character of the same bit stream. Accordingly, if any one of the S-bits of a newly assembled S-character is diiferentfrom the corresponding bit of the preceding S-character'of the same bit stream, an energizing signal will be fed from the exclusion-Or circuit 6% to flip-flop 64 to set the same to its 1 state. If the. compared S chanacters are the same, however, the flip-flop The flip-flop, once set, remains set until'the next clear signal. The clear signals are illustrated in the PEG; 4 waveform designated CLEAR.- 1

Summarizing the above operation, the coding of successive S -characters of the same bit stream are compared 7 by means of theexclusiveOr circuited. The iiip fi'opd will normally remaininits fO state, thereby preventing the delivery of read out pulsesto' the AND gates 59 via 1 gate 63. .However, upon a change in S-character coding,

' the exclusive-Or gate will deliver an energ zing signal to thefiip-fiopod toset the sameto its 1 state. Anenabling signal will therefore be fed to gate fifipermitting Y 1 the-sameto'pass a read out pulse. The flip-flop is then once again reset prior to the next read out pulse, and the operation is repeated as described.

'Referring'now to FIG. 8 of -the drawing'awherein parts corresponding toparts of FIG. 3 are correspondingly numbered, the delay loop here again comprisesa shift register '52 and a delay line 5 3 connected end toend in a loop configuration. The criterion forever-all loop delay islikewise the 'sl ame, i.e., adouhle sub-frame interval 1 -1 bitspacing in theflo'opQ in fact, except. for a reversal of the read in and read out operations, the structure and timingfrelatidriships of the FIG. 8 distributor are sub- Acco'nside'red in detail. I

The mode .of-oper tion ofthe distributor of FIG. 8 i can be best understood by reference to the table illustrated 1 l p in EEG. 9 of the drawings] In this table the vertical columns designate bit'positi ons in the delay loop; the

columns 9 1 'represent-theibit positions oiferedfby the shift register, while the remaining columns 92 represent thestorage capacity of the "delay line '53 in terms of bit positionsi f 1" he horizontallines -93 correspond symbolically .to the delivery'of advance'or shift pulses to the shift regis ter. l theright' and then read out or'recirculated in the loop Accordingly, each stored bit is shown. shifted to asfsuccessive advance pulses", symbolically represented by lines 93, are deliveredto the shift register.

i As in the assembler of F183,"acycleof'operation is initiated herein with the delivery of a reset signal to the counterofthe timing signal generator. circuit 30. The

resetisigna'l is shown'on'theftirne ordinate of the BIG, 9 table as-Jying betweentwo advance pulses, fthus correspondingto theflocaticn of' 'thel'same'in FIG. 4. Siinnlg tane'ous'with'the re'setfof the counter of the timing signal generator, the first S-character (S S S S is read into the shift register in parallel form. As indicated in FIG. 9, the 5 bit is inserted into stage (1) of register 52, the S bit is deposited in stage (2) and so on. The advance or shift pulse which follows the reset signal serves to shift these stored bits one bit position to the right. However, the first sampling pulse occur-s herein simultaneous with this advance pulse and hence the S bit which is advanced out of the register is delivered to the outgoing bus 50 via the enabled AND gate 51. The gate 57 is simultaneously inhibited, as heretofore described, and the s bit is thereby prevented from recirculating in the delay loop. This operation is illustrated symbolically in FIG. 9, the S hit being indicated as having been read out with the S S and S bits shifted one bit position to the right.

The next advance pulse again shifts the stored bits one bit position with the result that the S bit is read out of the register and into the delay line 53 via the gate 57. in FIG. 9, the S is shown shifted into the extreme lefthand bit position, which of course corresponds to the input of the delay line. This bit thereafter moves through the line at a rate corresponding to the shift rate. With successive shift pulses, the S and 8, bits will be shifted into the delay line and they will then proceed to traverse the length of the line, traveling as shown in FIG. 9 from left to right.

One half of an advance pulse period after the S bit is read out of the register and into the delay line, the next S-character (S S S S will be read into the shift register. The next succeeding advance pulse then serves to shift the S bit out of the register and since another sampling pulse occurs at this time, the S bit will be delivered to the outgoing bus St As in the assembler of FIG. 3, a sampling pulse occurs once for every fourth advance pulse, i.e., the shift register is advanced at a rate four times the sampling bit rate.

The mode of operation depicted in FIG. 9 should be clear at this point. The stored bits advance to the right at a rate corresponding to the shift rate. A sample pulse occurs for every fourth advance pulse and the bit that is in stage (1) of the register at that time is read out onto the outgoing bus 5t S-character read in takes placeat the instants indicated in FIG. 9. After the insert of the last S-character (S S S 5 into the register the bits circulate around the delay loop as explained. The stored bits precess with respect to the bit stream S will be inserted into register 52, and the described operation will thence repeat.

TheAND gates 17, 27, 37 and 47 are connected to the counter of the timing signal generator 36 in exactly the same manner as in FIG. 3. Accordingly, these gates are sequentially and cyclically enabled every double subframe interval. The sample pulses fed to the sampling gate 51 are also delivered to the input of these AND gates and, therefore, the sample pulses will be sequentially and cyclically routed to the respective output leads of AND gates 17, 27, 37 and 47.

The output of each AND gate 1'7, 27, 37 and 47 is fed to a double rail gate logic circuit such as described heretofore. The sampled S-bits on bus 550 are also coupled to each of these logic circuits. Accordingly, when the S bit, for example, is readout of the register 52- onto busSt), the associated sampling ulse .will be routed through the AND gate 17 to the output lead of the latter. The 5 bit is thus fed to the flip-lop 12 via one of the AND gates of the logic circuit 19. If this S-bit is a binary one it will be delivered to the set terminal of flip-flop 12 to set the same to its 1 state; whereas if the S bit is binary zero it will be routed via the inverter 14 and AND gate 15 to the reset terminal to thereby set the flip-flop 12 to its state.

In similar fashion, the S bit appears on bus 50 concurrently with the appearance of the next sampling pulse on the output lead of AND gate 27. Thus, the S bit will be fed to the flip-flop 22 via the logic circuit 29. The S bit is in the same manner coupled to the flip-flop 32, and the S bit is sent to flip-flop 42. The enabling of the AND gates 17, 27, 37 and 47 thereafter recycles and the S bits of the respective S-characters are routed to their respective flip-flops, and so on for the S and 8., bits.

Similar to the FIG. 3 assembler arrangement, each flip-flop of the FIG. 8 distributor is associated with a given message bit stream. Thus, the continuous setting and resetting of each flip-flop corresponds to the 5-bit coding intended for each bit stream. The flip-flop outputs are sampled at appropriate times and these-samples are delivered to the 8-bit inserters for insertion of the same into the respective outgoing message bit streams.

It should be clear at this point that the principles of the present invention are of general applicability and are in no way limited to the particular message bit stream format shown. For example, while the S-characters have been assumed for illustrative purposes to comprise four S-bits, the instant invention is quite obviously not limited thereto.

Accordingly, it is to be understood that the foregoing disclosure relates to only prefered embodiments of the invention and numerous .modifications and alterations may be made therein without departing from the spirit and scope of the invention.

What is claimed is: V v

1. In a time division switching system having a plurality of incoming time division multiplexed message bit streams that includesupervisory signal bits at uniformly spaced positions in each frame which form unique S- characters, a supervisory signal assembler comprising a delay line and a shift register connected end to end in ,a loop configuration, the total loop delay being equal to the time duration between successive signal bits in each message bit stream :1 bit spacing in the delay loop, means for sequentially and cyclically scanning the message bit streams for signal bits and delivering samples thereof to the input of said delay loop, and means'for reading assembled S-characters out of the delay loop after the last signal bit of each S-character has been inserted therein.

2. A supervisory signal assembler as defined in claim 1 including means for preventing the aforementioned read out of S-characters except in response to a change in the coding of the same.

3. In a time division switching system having a plurality of incoming time division multiplexed message bit streams that include supervisory signal hits at uniformly spaced positions in each frame which form unique S- characters, a supervisory signal assembler comprisinga delay line and a shift register connected end to end in a loop configuration, the total loop delay being equal to the time duration between successive signal bits in each message bit stream less one delay loop bit spacing, means tributor for distributing unique S-characters as signal bits to respective message bit streams, said distributor comprising a delay line and a shift register connected end to end in a loop configuration, the total loop delay being equal to the time duration between successive signal bit positions in each message bit stream :1 bit spacing in the delay loop, means for inserting Scharacters into aid delay loop, means for sampling the output of the delay loop at a predetermined uniform rate, and means for sequentially and cyclically routing the sampled signals to temporary storage means associated with each of the aforementioned message bit streams.

5. In a time division switching system having a plurality of incoming time division multiplexed message bit streams that include supervisory signal hits at uniformly spaced positions in each frame which form unique S-charcharacters and a plurality of outgoing. multiplexed message bitstreams including supervisory signal bit positions similarly uniformly spaced in each frame, a supervisory signal assembler and distributor combination therefor, said signal assembler and distributor each comprising a delay line and a shift register connected end to end in a loop configuration, the total delay of each loop being equal to the time duration between successive sign-a1 bit positions in each message bit stream :1 delay loop bit spacing, means for sequentially and cyclically scanning the incoming message bit streams for signal bits and delivering samples thereof to the input of the assembler delay loop, means for reading assembled S-characters out of the assembler delay loop after the last signal bit of each S-character has been inserted therein, means for inserting S-characters into the distributor del-ay loop, means for sampling the output of the distributor delay loop at :a predetermined uniform rate, and means for sequentially and cyclically routing the latter sampled signals .to tempor ary storage means associated with each of the aforementioned outgoing message bit streams.

6. A data processing system for assembling into S- characters the supervisory signal bits that are uniformly spaced in each frame of a plurality of incoming time separated message bit streams, comprising a shift register and a delay line connected end to end in a loop configuration, means for sequentially and cyclically scanning the incoming message bit streams for supervisory signal bits and delivering samples thereof to the input of said shift register, means for hifting'the sampled bits in said register at a rate which is a predetermined multiple of the the rate of sampling, the length of said delayline'being such as to cause the sampled bits which circulate around .the delay loop to precess one delay loop bit position for each circulation, and means for reading assembled S-characters out of the shift register immediately after the last sampled signal bit of each S-chanacter has been inserted therein.

7. A data processing system as defined'in claim 6 wherein the shift register comprises a number of stages qual in number to the number of signal bits forming the S-chanacters.

8. A data processing system as defined in claim 7 wherein the assembled signalbits forming the S-ch-aracters are read out of the shift, register in parallel form.

9. A data processing system as defined in claim 6 including means for inhibiting the reintroduction into the shift register of a circulating sampled signal bit during the insertion into the latter .of a newly sampled signal bit.

10. A data processing system as defined in claim 6 including means for inhibiting the aforementioned read out of S-characters except in response to a change in the coding of the same.

' 11. A data processing systemfor distributing the supervisory signal bits of a plurality of unique S-characters to respective outgoing time separated message bit streams, comprising a shift register and a delay line connected end to end in a loop configuration, said shift register has a number of stages equal in number to the number of sigl. 5 nal bits forming the S-characters, means for inserting the S-char-acters into said shift register in parallel form, means for successively applying shift pulses to said register to shift the signal bits stored therein, the length of said delay line being such as to cause the signal bits which circulate around the delay loop to precess one delay loop bit position for each circulation, means for sampling the output of the shift register at a predetermined rate which is a submulti-ple of and synchronous with the shift rate of the register, and means for sequentially and cyclically routing 10 1% the sampled signal bits to temporary storage means which are respectively associated with each of the aforementioned message bit streams.

12. A data processing system as defined in claim 11 including means for inhibiting the insertion into the delay line of a circulating signal bit during the sampling of the output of the shift register to thus terminate the circulation of the signal bit.

No references cited. 

1. IN A TIME DIVISION SWITCHING SYSTEM HAVING A PLURALITY OF INCOMING TIME DIVISION MULTIPLEXED MESSAGE BIT STREAMS THAT INCLUDE SUPERVISORY SIGNAL BITS AT UNIFORMLY SPACED POSITIONS IN EACH FRAME WHICH FROM UNIQUE SCHARACTERS, A SUPERVISORY SIGNAL ASSEMBLER COMPRISING A DELAY LINE AND SHIFT REGISTER CONNECTED END TO END IN A LOOP CONFIGURATION, THE TOTAL LOOP DELAY BEING EQUAL TO THE TIME DURATION BETWEEN SUCCESSIVE SIGNAL BITS IN EACH MESSAGE IT STREAM $1 BIT SPACING IN THE DELAY LOOP, MEAN FOR SEQUENTIALLY AND CYCLICALLY SCANNING THE MESSAGE BIT STREAMS FOR SIGNAL BITS ANDELIVERING SAMPLES THEREOF TO THE INPUT OF SAID DELAY LOOP, AND MEANS FOR READING ASSEMBLED S-CHARACTERS OUT OF THE DELAY LOOP AFTER THE LAST SIGNAL BIT OF EACH S-CHARACTER HAS BEEN INSERTED THEREIN. 